Pre-connectorized fiber optic distribution cable

ABSTRACT

A factory prepared fiber optic distribution cable has at least one predetermined access location for providing access to at least one pre-connectorized optical fiber. The fiber optic distribution cable includes at least one preterminated optical fiber withdrawn from a tubular body at the access location, a connector attached to the preterminated optical fiber, a transition piece for transitioning the preterminated optical fiber from the tubular body into a protective tube, and a protective shell encapsulating the access location for protecting the pre-connectorized optical fiber. Alternatively, the fiber optic distribution cable includes at least one preterminated optical fiber withdrawn from a tubular body, a transition piece for transitioning the preterminated optical fiber from the tubular body into a protective tube, a connector attached to the preterminated optical fiber, a plurality of cable centralizers, and a protective shell for encapsulating the access location and protecting the pre-connectorized optical fiber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a fiber optic distributioncable and, more particularly, to a factory assembled fiber opticdistribution cable having at least one predetermined access location forproviding access to at least one preterminated and pre-connectorizedoptical fiber.

2. Description of the Related Art

Optical fibers are used for a variety of applications including voicecommunication, data transmission and the like. With the ever-increasingneed for connecting remote locations to a fiber optic distributioncable, it is apparent that more efficient methods of performing amid-span access of a distribution cable are required. Typically, toperform a mid-span access, a technician must remove a portion of thecable sheath in the field at a convenient location along an installeddistribution cable. Once the sheath is removed, the technician mustaccess pre-selected optical fibers, sever the pre-selected opticalfibers and remove a length of the optical fibers from the distributioncable. The removed length of optical fiber provides the field technicianwith adequate length to splice one or more optical fibers of a cablecomprising a lesser amount of optical fibers than the distributioncable, typically termed a “drop cable,” to the distribution cableoptical fibers. After all splicing is complete, the accessed location istypically covered using an enclosure designed to protect the splices andthe section of the distribution cable with the sheath removed. This timeconsuming process is typically accomplished by a highly skilled fieldtechnician at a significant cost and under field working conditions.

Several approaches have been developed to overcome the disadvantages ofaccessing optical fibers in the field. In one approach, the splicing ofdrop cables to the distribution cable is performed at a factory duringthe manufacturing of the cable. The preterminated cable, including themain cable, drop cables and associated splice closures, are assembledand wound onto a cable reel to be delivered to an installation site.Accordingly, conditions for making high quality splices may be maximizedin the factory, thereby increasing splice quality and also reducing theexpense and difficulty associated with field splicing.

U.S. Pat. No. 5,121,458 (the '458 patent) issued to Nilsson et al. andentitled “Preterminated Fiber Optic Cable,” describes a preterminatedfiber optic cable having a main trunk cable comprising a plurality ofoptical fibers disposed therein, and multiple drop cables spliced to thetrunk cable at various branch points. The preterminated fiber opticcable is assembled at the time of manufacture and is installedthereafter. At each branch point, a splice closure is utilized forprotecting the optical fibers and splices from moisture and mechanicaldamage, providing a strong anchoring point for the optical fiber dropcable and insuring that the minimum fiber bend radius is not violated.While the preterminated fiber optic cable assembly described in theNilsson et al. patent is useful in certain applications, its use islimited to applications in which it is installed through a conduithaving an outer diameter of about 4 inches or greater. In addition, therelatively large outer diameter of the splice closure greatly hinderswinding the assembled cable onto a cable reel.

U.S. Pat. No. 5,528,718 (the '718 patent) issued to Ray et al. andentitled “Fiber Optic Cable System Including Main and Drop Cables andAssociated Fabrication Method,” describes an approach for reducing thesize of the branching point of the drop cables from the main cable. Thecable system is assembled in the factory and includes a main cable andone or more drop cables connected to the main cable at spaced apartlocations along the main cable. The drop cable is spliced to the maincable using a splice closure including a fiber guide that securesspliced together end portions of the respective optical fibers in alongitudinally extending direction and devoid of any slack coils ofoptical fiber. Accordingly, the overall diameter of the splice closureis reduced in size as compared to the splice closure of the Nilsson etal. patent, thereby permitting the cable system to be stored on a reeland to be readily installed through a conduit. A disadvantage of thissystem is that the outer diameter of the assembly exceeds the innerdiameter of the conduit through which the cable system is typicallyinstalled within when multiple drop cables are connected at a singlebranch point.

Accordingly, there continues to be an unresolved need for a factoryassembled, preterminated and pre-connectorized distribution cable thatreduces field installation costs and has an outer diameter that does notexceed the inner diameter of the conduit through which the cable systemis typically installed. As such, it is desirable to provide apre-connectorized fiber optic distribution cable including one or morepredetermined access locations having factory preterminated andpre-connectorized optical fibers along the length of the distributioncable. Further, it is be desirable to provide a pre-connectorizedfiber-optic distribution cable having the lowest possible profile, whilestill maintaining discrete fiber capability. It is also desirable in afiber-to-the-premises (FTTP) optical network to provide apre-connectorized access location in the mid-span of a distributioncable that is adapted to be readily deployed in the field with temporaryprotective components that are easily removed so that a permanentprotective closure may be added to the cable.

BRIEF SUMMARY OF THE INVENTION

To achieve the foregoing and other objects, and in accordance with thepurposes of the invention as embodied and broadly described herein, thepresent invention provides various embodiments of a factory assembled,pre-connectorized fiber optic distribution cable having at least onepredetermined access location for providing access to at least onepreterminated and pre-connectorized optical fiber. The factorypre-connectorized distribution cable may be wound upon a cable reel andinstalled through a conduit having a diameter of less than about 1.9inches. A particular advantage of this pre-connectorized distributioncable over conventional cable systems is the ability to readily connectpre-connectorized drop cables without fusion splicing in the field,which reduces labor time and cost, and lends itself to installationflexibility. Each access location has an outer diameter of less thanabout 1.9 inches, and more preferably, less than about 1.5 inches, andpresents at least one pre-connectorized optical fiber at the accesslocation for readily connecting at least one drop cable to thedistribution cable after installation. Another advantage of the presentinvention is the ability to utilize a variety of different closuredesigns to protect the factory prepared splices and connectors, and toanchor the drop cables.

In one embodiment, the pre-connectorized fiber optic distribution cablecomprises any fiber optic cable having at least one optical fiberdisposed within a tubular body, wherein the tubular body may include,but is not limited to, a buffer tube, a monotube or a tube formed from awater-swellable tape. In order to achieve a low profile mid-span access,a section of the cable sheath is removed in the factory to expose thetubular body within the distribution cable. For each access location,the appropriate tubular body may be accessed at one or more places alongthe exposed section of the tubular body. In embodiments in which thetubular body is a buffer tube, a known fiber access tool may be used topenetrate the buffer tube in at least two locations. Starting at theappropriate access point, pre-selected optical fibers are accessed andsevered. The remaining optical fibers remain intact and continue alongthe distribution cable. In embodiments in which the distribution cablecomprises a plurality of individual optical fibers, the pre-selectedoptical fibers may be fished out of a second access point in the tubularbody to thereby expose short lengths of the optical fibers. Inembodiments in which the distribution cable comprises ribbonized fibers(i.e., one or more fiber ribbons), a larger portion of the tubular body,and typically the entire portion of the tubular body within the removedsection of the cable sheath, may be opened in order to sever andseparate a number of pre-selected optical fibers from the ribbon.

In either case, the preterminated optical fibers may be routed through atransition piece and guided into one or more protective tubes secured tothe transition piece. The transition piece may be secured to astructural member (e.g., a strength member) of the cable or to thetubular body at the location where the optical fibers ultimately exitthe tubular body. The transition piece is thereby secured against torqueand may help seal the optical fiber exit point. The preterminatedoptical fibers are spliced in the factory to tight buffered or jacketedconnectorized optical fibers, (i.e., pigtails), so as to provide a totalpre-connectorized fiber length of at least about 20 inches. The accesspoints on the tubular body may be sealed using a heat shrinkablematerial, tubing or a self-fusing or self-amalgamating tape. A pluralityof cable centralizers are positioned at various intervals along thelength of the access location. The cable centralizers are operable forcentering the distribution cable within a protective shell and forrouting and protecting the pre-connectorized optical fibers. In oneembodiment, the protective shell is overmolded over the entire accesslocation. In an alternative embodiment, the protective shell is threadedonto the distribution cable, positioned over the entire access locationand secured. Diameter transition members are used to provide a smoothtransition between the outer diameter of the distribution cable and theouter diameter of the protective shell. End caps provide axial andtorsional resistance to the assembly. Heat shrinkable material with atleast one ripcord disposed underneath is positioned over the diametertransition members, end caps and a portion of the protective shell. Oncethe distribution cable is installed, the at least one ripcord may beused to remove the heat shrinkable material and protective shell inorder to expose the pre-connectorized optical fibers. In preferredembodiments, all components of the access location are designed suchthat they can be positioned on the distribution cable without having tofeed the components along the entire length of the distribution cable.

In another embodiment, the present invention provides apre-connectorized fiber optic distribution cable for use in an opticalnetwork. The pre-connectorized distribution cable comprises a pluralityof predetermined mid-span access locations along the cable length. Thepre-connectorized distribution cable may be readily deployed in anoptical network in an assembled and protected configuration, and theprotective components may be easily removed in the field and a closureadded to the distribution cable to conceal and protect eachpredetermined access location. In one embodiment, the pre-connectorizedoptical fibers may be connected inside the enclosure to an adapter orreceptacle provided in a connector port of the closure. Apre-connectorized drop cable from the optical network may then bereadily connected to the pre-connectorized optical fiber within theconnector port.

In a further embodiment, the present invention provides a method ofmid-span accessing a fiber optic distribution cable at a predeterminedaccess location to connectorize at least one optical fiber. The methodcomprises: (1) removing a length of the cable sheath to expose apredetermined length of at least one tubular body; (2) making a firstcut on the appropriate tubular body; (3) severing one or morepre-selected optical fibers at the location of the first cut; (4) makinga second cut on the appropriate tubular body about 9 to 12 inchesupstream from the first cut; (5) fishing the pre-selected and severedoptical fibers out of the second cut to present an optical fiber lengthof about 9 to 15 inches; (6) repairing the first cut point; and (8)splicing a pigtail to the optical fiber length to provide apreterminated and pre-connectorized optical fiber having a length of atleast about 20 inches.

In a still further embodiment, the present invention provides a methodof mid-span accessing a fiber optic distribution cable at apredetermined access location to connectorize at least one optical fiberof a fiber ribbon. The method comprises: (1) removing a length of acable sheath to expose a predetermined length of at least one tubularbody; (2) opening a predetermined length of the at least one tubularbody to expose a plurality of ribbon optical fibers; (3) severingpre-selected optical fibers; (4) separating the pre-selected and severedoptical fibers from the ribbon to present a predetermined fiber length;(5) splicing a pigtail to each optical fiber; and (6) covering andprotecting the uncut ribbon fibers.

In a still further embodiment, the present invention provides amulti-purpose tool for use with a pre-connectorized fiber opticdistribution cable as described herein that is operable for bothsecuring and removing the end caps, and for extracting the ripcords toremove the heat shrinkable material and the protective shell.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention are better understood when the following detailed descriptionof the invention is read with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a pre-connectorized fiber opticdistribution cable including a plurality of preterminated andpre-connectorized optical fibers in accordance with an exemplaryembodiment of the present invention;

FIG. 2 is a perspective view of the distribution cable of FIG. 1 furtherincluding a tubular body for protecting the pre-connectorized opticalfiber;

FIG. 3 is a perspective view of the distribution cable of FIG. 2encapsulated by a protective shell;

FIG. 4 is a perspective view of an alternative embodiment of apre-connectorized fiber optic distribution cable in accordance with anexemplary embodiment of the present invention;

FIG. 5 is an exploded view of the distribution cable of FIG. 4;

FIG. 6 is a perspective view of the distribution cable of FIG. 5 in theassembled configuration;

FIG. 7 is a perspective view of a cable centralizer defining an openingfor receiving a distribution cable and a plurality of optical fiberrouting slots in accordance with an exemplary embodiment of the presentinvention;

FIG. 8 is a perspective view of a multi-purpose tool operable for bothsecuring and removing an end cap, and extracting a ripcord of a fiberoptic distribution cable in accordance with an exemplary embodiment ofthe present invention; and

FIG. 9 is an illustration of the pre-connectorized fiber opticdistribution cable of the present invention installed within aconventional fiber optic communications network.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings in which exemplary embodiments ofthe invention are shown. However, this invention may be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. These exemplary embodiments are providedso that this disclosure will be both thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like reference numbers refer to like elements throughout the variousdrawings.

The pre-connectorized fiber optic distribution cable of the presentinvention comprises at least one predetermined access location along thecable length for providing access to at least one preterminated andpre-connectorized optical fiber. In preferred embodiments, thepre-connectorized distribution cable comprises a plurality of accesslocations at spaced apart locations along the cable length, thusproviding multiple access locations, also referred to herein as “tappoints,” for joining at least one pre-connectorized drop cable to thedistribution cable. The pre-connectorized fiber optic distribution cablemay be wound upon a reel for shipping and deployment in aerial andburied applications, such as through a bore or conduit. Thepre-connectorized distribution cable is assembled in a factory, thuseliminating the need for first installing a fiber optic cable and thenperforming a mid-span access, for example at a pole or pedestal in thefield. The pre-connectorized distribution cable of the present inventionoffers communication providers factory prepared, low profile accesslocations that are protected during the cable installation process andare removable once the cable is installed. Once the distribution cableis installed, the at least one pre-connectorized optical fiber may bereadily connected to a connector port of a conventional closure andthereafter connected to a pre-connectorized drop cable in an opticalcommunications network.

Referring now to FIG. 1, a perspective view of one embodiment of apre-connectorized fiber optic distribution cable is shown. Thepre-connectorized fiber optic distribution cable 20 includes at leastone tubular body 22 disposed within a cable sheath 24. As is known bythose skilled in the art, the distribution cable as shown and describedherein may include any known fiber optic cable having a fiber countgreater than that of an associated drop cable and comprising at leastone tubular body 22. The tubular body 22 may include, but is not limitedto, one or more buffer tubes, a monotube or a tube formed from awater-swellable tape. In one particular example, the distribution cableis an ALTOS® dielectric cable available from Corning Cable Systems LLCof Hickory, N.C. The ALTOS® dielectric cable, for example, is alightweight cable designed for both conduit (buried) and aerial (lashed)installations. In another example, the distribution cable is a StandardSingle-Tube Ribbon (SST-Ribbon™) cable available from Corning CableSystems LLC of Hickory, N.C. The SST-Ribbon™ cable contains readilyidentifiable twelve-fiber ribbons in a monotube. The distribution cablemay be of a loose tube design that provides stable performance over awide range of temperatures and is compatible with any telecommunicationsgrade optical fiber. The distribution cable may comprise awater-blocking compound, such as a gel, to prevent water penetrationthat may lead to optical fiber damage. However, the distribution cablemay also be a “dry-tube” cable. In preferred embodiments, thedistribution cable is flexible, easy to route and has no preferentialbend.

The exposed and preterminated 250 μm optical fibers 26 are shown beingrouted through an optical fiber transition piece 28 that is secured to900 μm protective tubes 30. In preferred embodiments, the transitionpiece 28 and the protective tubes 30 are assembled and secured togetherusing an epoxy material prior to inserting the optical fibers 26 intothe protective tubes 30. In one method of assembly, an optical fiberlength of about 9 to 15 inches is withdrawn from the tubular-body 22,routed through an optical fiber opening (not shown) formed in thetransition piece 28, and inserted into the protective tubes 30. Thetransition piece 28 may be secured to the tubular body 22 or to astructural member of the distribution cable, for example, at least onestrength member (not shown).

The transition piece 28 may be rigid or somewhat flexible to permit thetransition piece 28 to bend slightly to conform to the curvature of thetubular body 22 or other structure to which it is attached. Thetransition piece 28 is positioned to cover the exit point and to protectthe open portion of the tubular body 22. In one embodiment, thetransition piece 28 is snapped over the region of the tubular body 22.Once all of the optical fibers 26 have been routed, the opening providedin the transition piece 28 may be filled with a sealing material, suchas a silicone elastomer or epoxy material, to seal the transition point,prevent torque in the transition piece 28 and prevent any water-blockinggel that may be present from leaking out of the tube.

In a particular embodiment, the transition piece 28 is a molded piecedefining an optical fiber opening for receiving the optical fibersexiting from the tubular body 22. The transition piece 28 furtherdefines an opening for routing the optical fibers into an optical fiberslot. The optical fiber slot is operable for maintaining the opticalfibers in a linear array and securing the protective tubes 30. Thetransition piece 28 may be specifically designed to transition eitherfour or eight optical fibers from the tubular body 22 into protectivetubes 30. One optical fiber slot may be used in applications in whichone to four optical fibers are withdrawn from a tubular body 22. Anotheroptical fiber slot may be used in applications in which five to eightoptical fibers are withdrawn from the tubular body 22. The appropriateoptical fiber slot should be positioned downstream of the origination ofthe optical fibers so that the optical fibers are transitioned smoothlywithout violating their minimum bend radius.

In one embodiment, the preterminated optical fibers 26 may be directlyconnectorized. This process involves mounting connectors directly on tothe ends of the preterminated optical fibers 26 withdrawn from thetubular body 22, resulting in an optical fiber length of about 9 to 15inches. However, in preferred embodiments and specifically in theembodiments shown throughout the figures, the preterminated opticalfibers 26 are spliced, preferably fusion spliced, to buffered orjacketed pigtails having a predetermined length in order to provide atotal optical fiber length of at least about 20 inches. In the splicedconfiguration, at least about a 10 inch length of optical fiber uponwhich a connector 32 has been previously mounted (i.e., a pigtail) maybe spliced in the factory to the withdrawn length of optical fiber 26.The splice points may be protected using splice protectors 34, which areoperable for holding and protecting the splice connection between theend of the preterminated optical fiber and the pigtail. The spliceprotectors 34 define a lengthwise extending passageway and are typicallyformed of a plastic material. One advantage of factory-installingspliced pigtails is that all connectors should have substantiallyconsistent optical properties.

In both spliced and direct connectorized embodiments, connector typesmay include, but are not limited to, SC, LC, FC, ST, SC/DC, MT-RJ, MTPand MPO ferrules. Whether or not the optical fibers 26 are individualfibers or fiber ribbons does not limit the connector type, however, invarious embodiments, MT-RJ, MTP and MPO ferrules may be used when thedistribution cable comprises fiber ribbons.

A plurality of resilient cable clips 36 may be positioned at desiredintervals along the length of the access location. The cable clips 36are operable for holding the distribution cable and a connector monotubeand centering the cable assembly within an over-molding tool, asdescribed below. The cable clips 36 may be added to the cable mid-spanat any time during the assembly process. The cable clips 36 aretypically formed of a thin metal material and define a channel forreceiving the connector monotube.

The pre-connectorized cable 20 further includes a cable clamp 38positioned at each end of the access location and over the cable sheath24. The cable clamps 38 protect the cable assembly by providingresistance to lateral and torsional forces that the assembly may beexposed to. The cable clamps 38 may further be operable for securing oneend of at least one ripcord 40. The cable clamps 38 provide an anchorand allow the at least one ripcord to be extracted opposite the clampedend in order to remove any heat shrinkable material or protectiveoverlayer. The cable clamps 38 may be secured on the distribution cableby any conventional fastener, such as a screw, rivet or clamp.

Referring to FIG. 2, the distribution cable 20 of FIG. 1 is shownincluding a connector monotube 42 for housing and protecting theconnectors and optical fibers 26 during installation of the distributioncable. In a preferred embodiment, the connector monotube 42 is comprisedof a flexible material, such that the connector monotube 42 is crushresistant. The connectors (32, FIG. 1) may be held within the connectormonotube 42 in a staggered configuration in order to minimize the outerdiameter of the connector monotube 42 and the overall outer diameter ofthe pre-connectorized distribution cable 20. The connector monotube 42is installed after the pigtails have been spliced and is retained withinthe plurality of resilient cable clips 36. The connector monotube 42defines a lengthwise extending passageway and is of a length sufficientto house the optical fibers 26, their respective protective tubes 30 andtheir respective connectors 32 originating from the transition piece 28.

Referring to FIG. 3, the pre-connectorized distribution cable 20 isshown in an assembled configuration. In one embodiment, a protectiveshell 44 formed by an over-molding process is operable for protectingthe pre-connectorized optical fibers 26 and connectors 32 during theinstallation process, and until the access location is utilized in theoptical network. At least one ripcord 40 extends a suitable distancebeyond the access location at each end of the protective shell 44. Asshown, a pair of ripcords 40 is shown spaced about 180 degrees apart.The at least one ripcord 40 is operable for removing the protectiveshell 44 after cable installation. Disposed immediately underneath theprotective shell 44 is an overmolding wrap (not shown) that preventspenetration of the molding material. In a preferred embodiment, theover-molding wrap provides a seal for all components disposed within theprotective shell 44, including the cable clamps 38. In an alternativeembodiment, a crush-resistant strength member (not shown) may bedisposed as necessary between the components and the overmolding wrap.

To overmold the access location, the distribution cable 20 is clampedinto a tool (not shown) that defines cavities into which the moldingmaterial flows. The distribution cable 20 is centered within theinternal cavity of the tool. The tool comprises a plurality of injectionports for injecting the molding material. The molding material mayinclude, but is not limited to, any polymeric material that may beinjected in a liquid form and will set-up to form a substantiallyhardened protective shell, e.g., a two-part polyurethane orthermoplastic material. The molding material will flow into any voidbetween the tool and the distribution cable 20. The cable clips 36 mayaxially center the assembly within the overmolding tool. A bottom centertangent point and the ends of each cable clip 36 may form a position inspace to provide for an even thickness of the mold. The overmoldedmaterial bonds to the over-molding wrap, the cable clamps 38 and about a1 to 2 inch section of the cable sheath 24 at each end of the accesslocation to form the protective shell. The protective shell 44 isremoved after cable installation by pulling the at least one ripcord 40through the overmolding wrap and removing the protective shell 44 toexpose the connector monotube. The connector monotube 42 may then beremoved to expose the pre-connectorized optical fibers 26 and connectors32.

In an alternative embodiment of the present invention, the protectiveshell 44 may comprise a crush-resistant monotube that may be threadedonto the distribution cable as previously described. The crush-resistantmonotube may be positioned and secured in place using a plurality of endcaps and heat shrinkable material. The crush-resistant monotube servesthe same intended purpose as the protective shell 44. The heatshrinkable material and crush-resistant monotube may be removed by atleast one ripcord disposed underneath in the manner previouslydescribed. Alternatively, the crush-resistant monotube may be formed asa clamshell or a pair of split halves with or without the end caps andadded to the distribution cable mid-span. As a result, the manufacturingprocess is simplified since the monotube need not be threaded onto thedistribution cable. The crush-resistant monotube or the monotube and endcaps may then be secured in place over the access location using a heatshrinkable material. It is also possible that the clamshell or splithalves can be pre-molded and positioned over the access location, and inparticular, the exposed portion of the tubular body 22, the transitionpiece 28, the optical fibers 26, the protective tubes 30, the connectors32, and if utilized, the connector monotube 42. The pre-molded clamshellor split halves may then be temporarily secured and overmolded with athin layer of molding material in the manner previously described. As aresult, the amount of molding material required to form the protectiveshell 44 may be substantially reduced and the cable clips 36 eliminated.

Referring now to FIG. 4, a perspective view of another embodiment of apre-connectorized distribution cable according to the invention isshown. The pre-connectorized fiber optic distribution cable 50 includesat least one tubular body 22 disposed within a cable sheath 24. Thetubular body 22 may include, but is not limited to, a buffer tube, amonotube or a tube formed from a water-swellable tape. Exposed andpreterminated 250 μm optical fibers (not shown) are routed through afiber transition piece 28 that is secured to the tubular body 22 or to astructural member of the distribution cable 50. Preferably, thepreterminated optical fibers are spliced to pigtails as previouslydescribed.

The pre-connectorized cable 50 further includes a plurality of cablecentralizers 46 positioned at desired intervals along the length of theaccess location. The cable centralizers 46 are operable for centeringthe distribution cable 50 within a protective monotube (not shown). Thecable centralizers 46 are also operable for routing and protecting theoptical fibers. The cable centralizers 46 may be designed to accommodatea variety of distribution cable diameters. The distribution cable 50remains centered by the cable centralizers 46 during assembly and cableinstallation. The pre-connectorized cable 50 further includes aconnector holder 48 for retaining a plurality of connectors (not shown)radially around the distribution cable 50. Preferably, the connectorholder 48 is made of a hardened material and defines a plurality ofslots for receiving the connectors. Preferably, the connector holder 48is a two-piece design that is added to the assembly mid-span. However,the connector holder 48 may be threaded onto the distribution cable 50prior to assembly.

An end cap 49 and a diameter transition piece 52 may be positioned ateach end of the access location. The end cap 49 is preferably atwo-piece component secured around the distribution cable 50 and overthe cable sheath 24 by a fastening mechanism, such as screws. The endcap 49 defines a shoulder 54 for receiving a crush-resistant monotube(not shown) and maintaining the position of the monotube once installed.The end cap 49 is also operable for protecting the cable assembly byproviding resistance to axial and torsional forces that the assembly maybe exposed to. The end cap 49 may also provide an anchoring point forsecuring one end of at least one ripcord, allowing the at least oneripcord to be extracted opposite the clamped end in order to remove anyheat shrinkable material or protective overlayer. The diametertransition piece 52 is preferably comprised of an elastomeric materialand is C-shaped, thereby allowing it to be added mid-span. The diametertransition piece 52 provides a smooth transition between the outerdiameter of the cable sheath 24 and the outer diameter of thecrush-resistant monotube.

Referring to FIG. 5, an exploded view of the pre-connectorizeddistribution cable 50 of FIG. 4 is shown, including a crush-resistantmonotube 56. The monotube 56 for protecting the access location duringdistribution cable installation is preferably comprised of a flexiblematerial such that the monotube 56 is crush resistant. The monotube 56defines a lengthwise extending passageway and is of a length sufficientto house the entire access location. The monotube 56 may be removed fromthe distribution cable 50 entirely, or slid down the distribution cablewhen the access location is utilized. To enter the access location, heatshrinkable material 58 disposed at each end of the access location isfirst removed. The heat shrinkable material 58 may be positioned andsecured in place over a portion of the cable sheath 24, the diametertransition piece 52, end cap 49 and a portion of the crush-resistantmonotube 56. At least one ripcord, as previously described, may be usedto remove the heat shrinkable material 58. An additional section of heatshrinkable material 60 may also be used to repair the exposed tubularbody 22 within the access location.

Referring to FIG. 6, the pre-connectorized distribution cable of FIG. 4is shown in an assembled configuration. The crush-resistant monotube 56and the heat shrinkable material 58 seal and protect the access locationduring the installation process, and until the access location isutilized in the optical network. Once accessed, at least onepre-connectorized optical fiber is presented for readily connecting atleast one pre-connectorized drop cable to the distribution cable 50. Theoverall outer diameter of the access location is less than about 1.9inches, and more preferably, less than about 1.5 inches.

Referring now to FIG. 7, a perspective view of a pair of connected cablecentralizers 46 is shown. The cable centralizers 46 are secured aroundthe distribution cable by mating the two substantially symmetricalhalves together via a fastening feature (not shown) defined by eachcable centralizer 46. In various examples, the fastening feature maycomprise a lock-and-key feature, a screw, a snap-fit or a clip. Eachcable centralizer 46 defines a central opening 62 for receiving thedistribution cable. Each cable centralizer 46 further defines at leastone optical fiber routing slot 64 preferably positioned adjacent itsouter periphery for routing the preterminated and pre-connectorizedoptical fibers along the length of the access location. The cablecentralizers 46 are typically formed of a plastic or metal materialcapable of providing crush protection to the distribution cable androuted optical fibers. Each cable centralizer 46 further defines agroove around its outer diameter for receiving a resilient band 66. Theresilient band 66 is placed around the cable centralizer 46 after theoptical fibers have been routed through the at least one routing slot 64in order to maintain the optical fibers within the slot 64 duringassembly and cable installation.

Referring now to FIG. 8, a multi-purpose tool 68 operable for bothsecuring and removing the end caps, and extracting a ripcord is shown.In one embodiment, a tool 68 is provided that comprises an elongatedbody having a tool tip 70 at one end and an engagement shank 72 at theopposite end. A first portion of the body adjacent the tool tip 70 has afirst diameter for engaging a fastener (e.g., a screw) of an end cap,and a second portion between the first portion and the engagement shankhas a second diameter that is greater than the first diameter. A slot 74adjacent the tip 70 is operable for engaging a ripcord. When extracted,the ripcord is wound around the second portion. The engagement shank 72may be inserted into the chuck of a drill or other rotating devicecommonly known in the art.

To achieve a mid-span, low profile access location with a distributioncable comprising individual optical fibers within a tubular body, asection of the cable sheath is severed and removed to expose the atleast one tubular body within the distribution cable. The exposed lengthof the tubular body may vary. However, in a preferred embodiment, thelength ranges between about 9 and 15 inches. The cable sheath may bering cut and removed using a tube access tool operable for slitting thecable sheath without damaging the tubular body disposed within thecable. As described above, the exposed length of the tubular body allowsfor about 9 to 15 inches of optical fiber to be withdrawn from thetubular body for direct connectorization or subsequent splicing.

For a given access location, the appropriate tubular body may beaccessed in at least two places using a standard No-Slack Optical FiberAccess Tool (NOFAT) available from Corning Cable Systems LLC of Hickory,N.C. The NOFAT tool is suitable for use in situations in which a minimala mount of tubular body slack can be accessed. The NOFAT tool provides aguide that allows a scalpel to open a section of the tubular bodywithout cutting completely through the tubular body or the opticalfibers disposed within the tubular body. The NOFAT tool is compatiblewith standard Corning Cable Systems ALTOS® Cable tube sizes.

As described herein, two access locations, typically about 9 to 15inches apart, are cut on the tubular body. As will be understood bythose skilled in the art, at least two access locations are specificallyadvantageous for removing one or more optical fibers from a tube filledwith a water-blocking gel. Starting at the first tube access point, apredetermined number of 250 μm optical fibers are accessed and severed.In a tube comprising twelve optical fibers, for example, four or eightoptical fibers may be preterminated. The remaining optical fibersdisposed within the tube remain intact and continue through thedistribution cable. The severed optical fibers are then fished out ofthe second access point, on the same tube, exposing about 9 to 15 inchesof optical fiber length. The minimum bend radius of the optical fibersshould not be violated during the process of fishing-out the fibers.After removing the optical fibers from the tube, any water-blocking gel(if present within the buffer tube) is cleaned off of the entire exposedlength of the optical fibers.

To achieve a mid-span, low profile access location with cablescomprising ribbon fibers within a tubular body, a complete portion ofthe cable sheath and tubular body is severed and removed to expose thefiber ribbons. The exposed length of the tubular body may vary. However,in a preferred embodiment, the length of the tubular body ranges betweenabout 9 and 15 inches. Starting at the downstream end of the fiberribbons, a predetermined number of 250 μm optical fibers are accessedand severed. In a ribbon comprising twelve optical fibers, for example,four or eight optical fibers may be preterminated. The remaining opticalfibers remain intact and continue through the distribution cable. Thesevered optical fibers are then separated from the ribbon, presentingabout 9 to 15 inches of optical fiber length. The minimum bend radius ofthe optical fibers should not be violated during the process of severingor separating the optical fibers.

In both methods of accessing the optical fibers, the tubular body andcable sheath are repaired using a heat shrinkable material. In apreferred embodiment, the heat shrinkable material is glue-lined toprovide a more secure repair. The heat shrinkable material providessealing and protection of the access point at which the optical fiberswere severed. Alternatively, the cable sheath and tubular body may berepaired with a self-fusing or a self-amalgamating tape in a knownmanner.

FIG. 9 illustrates the pre-connectorized fiber optic distribution cable20 according to the invention installed within a conventional fiberoptic communications network. In particular, the optical fibers 26accessed at one of the predetermined access locations along the fiberoptic distribution cable 20 are routed out of the transition piece 28and into the corresponding protective tubes 30. The optical fibers 26are then spliced to pigtails comprising connectors 32 and protected bysplice protectors 34 as previously described. Each connector 32 may berouted to a connector port 86 and connected to a respective connector 75of an optical fiber drop cable 76. A conventional outside plant closure82 is provided with a pair of through ports 84 for sealingly receivingthe distribution cable 20 and the connector port 86 for sealinglyreceiving the connector 32 and the connector 75 of the drop cable 76.Preferably, the drop cable 76 is pre-connectorized and comprisesconventional a single or multiple fiber connector 78 for connecting oneor more of the optical fibers 26 of the distribution cable 20 torespective optical fibers of the communications network within anoptical network connection terminal 80, such as a local convergencecabinet (LCC), a pedestal, a network access point (NAP), or a networkinterface device (NID) of the types available from Corning Cable SystemsLLC of Hickory, N.C.

The foregoing is a description of various embodiments of the inventionthat are provided here by way of example only. Although thepre-connectorized fiber optic distribution cable and method of assemblyhave been described with reference to preferred embodiments and examplesthereof, other embodiments and examples may perform similar functionsand/or achieve similar results. All such equivalent embodiments andexamples are within the spirit and scope of the present invention andare intended to be covered by the appended claims.

1. A fiber optic distribution cable having at least one predeterminedaccess location along the distribution cable for providing access to atleast one pre-connectorized optical fiber, the distribution cablecomprising: at least one preterminated optical fiber withdrawn from thedistribution cable at the access location; a connector attached to thepreterminated optical fiber; and a protective shell encapsulating theaccess location to protect the pre-connectorized optical fiber.
 2. Thedistribution cable of claim 1, wherein the protective shell is formed byan overmolding process.
 3. The distribution cable of claim 1, whereinthe protective shell comprises a monotube having a crush resistantproperty that is threaded onto the distribution cable and positionedover the access location.
 4. The distribution cable of claim 1, whereinthe outer diameter of the protective shell is less than about 1.5inches.
 5. The distribution cable of claim 1, wherein the protectiveshell is sufficiently flexible to permit the fiber optic distributioncable to be installed trough a conduit having an inner diameter of atleast about 1.9 inches.
 6. The distribution cable of claim 1, whereinthe preterminated optical fiber is spliced to a connectorized opticalfiber and the spliced together length of the preterminated optical fiberand the connectorized optical fiber is at least about 20 inches.
 7. Thedistribution cable of claim 1, further comprising a plurality of cableclips adapted for attachment to the distribution cable and operable forcentering the distribution cable within an overmolding tool.
 8. Thedistribution cable of claim 1, further comprising at least one ripcorddisposed underneath the protective shell and operable for removing theprotective shell to expose the at least one pre-connectorized opticalfiber.
 9. A fiber optic distribution cable having at least onepredetermined access location for providing access to at least onepre-connectorized optical fiber, the distribution cable comprising: atubular body for containing a plurality of optical fibers; at least onepreterminated optical fiber withdrawn from the tubular body at theaccess location; a transition piece adjacent the tubular body andoperable for transitioning the preterminated optical fiber from thetubular body and into a protective tube; a connector attached to thepreterminated optical fiber; a plurality of cable centralizers eachdefining a central opening for receiving the distribution cable and atleast one routing slot for receiving an optical fiber; and a protectiveshell encapsulating the access location and the cable centralizers toprotect the preterminated optical fiber and the connector.
 10. Thedistribution cable of claim 9, further comprising: an end cap positionedon the distribution cable adjacent each end of the access location; anda diameter transition piece adjacent each end of the access locationextending between the outer diameter of the distribution cable and theouter diameter of the end cap.
 11. The distribution cable of claim 9,wherein the protective shell is formed by an overmolding process. 12.The distribution cable of claim 9, wherein the protective shellcomprises a monotube having a crush resistant property that is threadedonto the distribution cable and positioned over the access location 13.The distribution cable of claim 9, wherein the outer diameter of theprotective shell is less than about 1.5 inches.
 14. The distributioncable of claim 9, wherein the protective shell is sufficiently flexibleto permit the fiber optic distribution cable to be installed through aconduit having an inner diameter of at least about 1.9 inches.
 15. Thedistribution cable of claim 9, wherein the preterminated optical fiberis spliced to a connectorized optical fiber and the spliced togetherlength of the preterminated optical fiber and the connectorized opticalfiber is at least about 20 inches.
 16. The distribution cable of claim10, further comprising a heat shrinkable material for sealing thediameter transition piece, the end cap and the access location.
 17. Thedistribution cable of claim 9, further comprising at least one ripcorddisposed underneath the protective shell and operable for removing theprotective shell to expose the at least one pre-connectorized opticalfiber. 18-28. (canceled)